Today there are several methods to record electrical spark discharges in the atmosphere, occurring within a thundercloud, between clouds and/or between a cloud and the ground.
The first method of monitoring storm activity is based on optical satellite observations of lightning occurring, as mentioned earlier, within thunderclouds, between the clouds and/or between the clouds and the ground. The method provides detailed information from an area that is observed directly by instruments mounted on a satellite. The zone observed covers ca. 105 km2, which constitutes only a small part of the Earth's surface. The orbital observation system, even with a broadly expanded network of satellites cannot ensure a reliable storm activity global monitoring system.
The second method of tracking storms is associated with the detection of electromagnetic signals within VLF, HF, and VHF radio frequencies, generated during the electrical spark discharges in the atmosphere. This method allows an assessment of discharge intensity and their location. Its disadvantage, however, is a range the signals, which—within these frequencies—is limited for distances up to several hundred kilometers within HF, and several thousand kilometers within VLF. Covering large areas to allow observation using stations requires a dense network of tracking stations. At present, the most developed monitoring system carries out analyses of signals registered simultaneously within VLF and HF frequencies. It operates only in highly-developed countries, thus it covers only a small percentage of the Earth surface.
The third method is based on tracking signals within VLF only. The range of a single station is up to one thousand kilometers. Currently, the world system is based on 27 measuring stations.
Propagation of electromagnetic field signals of extremely low frequency (ELF) is known from published results of research conducted by scientists of the Jagiellonian University, Krakow, Poland, presented in the paper titled “Studies of ELF propagation in the spherical shell cavity using a field decomposition method based on asymmetry of Schumann resonance curves”, Journal of Geophysical Research, Vol. 111, A10304, doi:10.1029/2005JA011429, 2006. In conformity with the thesis presented in this paper the curve asymmetry and the variability of the peak resonance frequencies in the observed ELF spectra arise from superimposition of the standing wave field, which create the resonance modes with the field of wave travelling out from the sources. The problem to be solved was whether it was possible to separate components of both fields and to measure them independently in the resonator. A new approach to this issue has been proposed and it consists in the measuring of spectrum asymmetry or a signal spectrum obtained by the observation of components of the electrical field or magnetic field with a single antenna. In this approach it was assumed that the signal spectrum in any point of the resonator includes a symmetrical part related to the resonance component field and a nonsymmetrical part connected with the travelling wave field. The power spectrum of a field component |a(θ, f)|2 has been determined using the formula:
                          a        ⁡                  (                      θ            ,            f                    )                            2    ≈            ∑              k        =        1            K        ⁢                                        p            k                    ⁡                      (            θ            )                          ·                  ⌊                      1            +                                                            e                  k                                ⁡                                  (                  θ                  )                                            ·                              (                                  f                  -                                      f                    rk                    *                                                  )                                              ⌋                                      (                      f            -                          f              rk              *                                )                +                              (                          γ              k              *                        )                    2                    
This formula enables the determination of the approximate distance θ from any point of a resonator to a single progressive wave source.
The observation methods of atmospheric discharges discussed above, even assuming a considerable expansion of the observation base, do not enable global monitoring of storm activity over the entire surface of the Earth. Also, none of the above methods guarantees a 100% detection efficiency of electrical spark discharges in the atmosphere. It is currently estimated that the effectiveness of methods mentioned is between 60 and 80 percent, depending on the method applied, and the signal analysis algorithms used.